1. Field of the Invention
The present invention relates to a method of and an apparatus for cleaning and separating wafers which are bonded on a fixing member in the form of an ingot by means of an adhesive, and then sliced by a wire saw in a direction perpendicular to a longitudinal dimension to form a row of wafers.
2. Discussion of the Related Art
As is generally known, in preparing wafers of a semiconductor material, a magnetic material and ceramics, etc., these materials are bonded on a fixing member in the form of an ingot, and then sliced utilizing a wire saw from a direction perpendicular to the longitudinal dimension to form a row of wafers.
Usually, the slicing by the wire saw is performed while spraying a slurry-like grinding liquid, and, after the material has been completely sliced, further performed to such a depth to reach a part of the fixing member. For this reason, the row of wafers after the slicing are bonded on the fixing member through the adhesive and smeared with the grinding liquid, and the grinding liquid enters among the adjacent wafers.
To obtain each wafer from this row of wafers, a plurality of wafers are manually separated from the fixing member, and then these plurality of wafers are manually separated one at a time. Thereafter, each wafer is cleaned to remove the grinding liquid.
The above-described separating operation, however, includes a process in which an operator flexibly separates a suitable number of wafers in accordance with the bonding condition of the wafers, and makes automation difficult.
That is, generally speaking, wafers are highly fragile, and since such wafers are glued together, it has been a technical problem as to how to separate them from each other by using a small force without causing any strain to the wafers.
The manual operation is advantageous in that it allows subtle adjustment in applying forces in accordance with the gluing condition, and it is difficult to replace this by a mechanical operation. Further, the requisite cost would be rather high.
In addition, in the above-described method, the row of wafers smeared with the grinding liquid must be handled in separating a plurality of wafers from the row of wafers. The wafers smeared with the grinding liquid is difficult to be mechanically handled, and make automation further difficult. Moreover, the grinding liquid contaminates devices.
Therefore, there is a demand for the development of a method which is suited for automation of the above process. In order to facilitate automation and keep the devices as clean as possible, a removal of the grinding liquid at an early stage has been requested.